Gaseous electric discharge lamp device



Nov. 12, 1935. w. UYTERHOEVEN ET AL GASEOUS ELECTRIC DISCHARGE LAMP DEVICE Filed Oct. 30, 1934 iNVE NTORS Wd/l ZZ W4 A ORNEY Patented Nov. 12, 1935 UNITED STATES PATENT oerce Willem Uyterhoeven, Martinus van Dam, and

Cornelia Verburg, Eindhoven, Netherlands, as signors to General Electric Company, a corporation of New York Application October 30, 1934, Serial No. 750,714 In Germany November 6, 1933 6 Claims. (Cl. 176-122) The present invention relates to gaseous electric discharge lamp devices generally and more particularly the invention relates to such devices the gaseous atmosphere of which consists of or comprises the vapor of a difficultly vaporizable metal i. e. a metal having a vapor pressure of less than 1 mm. at a temperature of 200 C., such as sodium, cadmium, thallium, or zinc.

Heat conservators, such as an evacuated envelope enclosing the lamp container, or a double walled jacket having the space between the inner and outer walls thereof evacuated and in which the lamp container is mounted, which reduce the transfer of heat from the lamp container to the ambient atmosphere and thus maintain the container at an elevated temperature are useful in obtaining an effective vapor pressure in such devices, that is a vapor pressure such that the spectrum of the light emitted by the device is rich in rays characteristic of the metal vapor during the operation of the device.

The vapor pressure in vapor lamps generally is determined by the lowest temperature in the lamp and the heating of parts of the lamp above the temperature of the part thereof having the lowest temperature has no effect on the vapor pressure. Indeed in a lamp having difllcultly vaporizable material therein excess heating of parts of the container may be harmful to the lamp device since even the part of the container whichis at the lowest temperature during the operation of the lamp must have an elevated temperature in order to have an effective vapor pressure in the lamp and when other parts of the lamp container are heated greatly above this temperature there is danger of the metal vapor attacking the glass chemically or of the glass becoming soft and the container collapsing. An appreciable amount of energy is also wasted in such useless heating of parts of the lamp container.

In a lamp device having a container made up of straight sections connected by a curved section or sections, such as a U-shaped container, the curved section is usually at a lower temperature than the straight sections during the operation of the device due to the larger heat radiating area thereof.

The object of the present invention is to provide a lamp unit comprising a gaseous electric discharge lamp device having a container consisting of straight portions and curved portions and a heat conservator in which all parts of the lamp container are at approximately the same temperature during the operation of the device.

Still further objects and advantages attaching to the device and to its use and operation will be apparent to those skilled in the art from the following particular description.

In accordance with this object the invention 5 comprises a coating which is a good heat interceptor either by virtue of its good reflecting qualities or by virtue of its poor heat conductivity characteristics, which coating is in operative relation to the curved part of the container to reduce the dissipation of heat therefrom. In one embodiment of the invention the coating is applied to the curved part of the container. In another embodiment of the invention the coating is applied to the part of the walls of the heat conservator adjacent the curved part of the lamp container. By reducing the dissipation of heat from the curved portion of said container the temperature of said curved portion is made approximately that of the straight portions of said container during the operation of the device.

In the drawing accompanying and forming part of this specification an embodiment of the invention is shown in a front elevational, partly sectional view.

Referring to the drawing the new and novel lamp unit comprises a gaseous electric discharge lamp device having a U-shaped container l and a double walled jacket 4 having the space between the inner and outer walls thereof evacuated. Said container I has an electrode 2 sealed therein at each end thereof, a starting, rare gas therein, such as argon or neon, at a pressure of approximately 1 to 10 mm. and a quantity of vaporizable material therein, such as sodium. Said electrodes 2 are electron emitting when heated and consist of a metal filament, such as a tungsten filament, having another filament, such as a tungsten or a nickel filament, wrapped around said first named filament and a coating of electron emitting material, such as barium oxide, applied to said filaments. Said electrodes 2 are heated to an electron emitting temperature by the discharge current. Said container I has a bayonet base 3 cemented to one end thereof and the other end of said container I is covered by said base 3 but is free to move therein. Said container I thus can contract and expand freely during the life of the lamp device without danger of fracturing the walls thereof.

The jacket 9 has a ring-base 5 of insulating material cemented thereto and said base 5 frictionally engages with said base 3 andis locked in position thereon by the pin 6.

The outer surface of-the curved, lower portion I of container l has a thin coating I oi. reflecting material, such as silver, thereon which coating 1 reflects the heat of said curved'part and thus reduces the dissipation of heat from said curved part so that the temperature of said curved part is made approximately that of the straight parts at said container i during the operation oi said lamp unit.

When desired, the coating l is omitted from thecurved part of the container I and a similar coating 8 (indicated in dotted lines) is applied to one or both of the walls oi the rounded, end part oi the jacket d adjacent the curved part of the container i and on the side of said walls facing said curved container part. In this case the coatings d reflect back to the container i an appreciable part of the heat radiated by the container i with the result pointed out above. It is also efiective to apply a reflecting coating similar to the coatings 8 to the inner surface of the inner wall oi the jacket, that is, the surface facing the outer wall of said jacket 5, which reduces the radiaticn of heat from said inner wall.

We prefer that the silver coating be a dustlike deposit, or a very thin film which transmits all the visible light emitted by the lamp device but which reflects all the infra-red, or heat rays emitted by the device. Such a coating is applied to the lamp container, or the heat conservator, by methods well known in the art, such as by chemical deposition or cathode sputtering.

When desired the coatings i and 8 consist of a material having poor heat conductivity characteristics, such as a thin layer of asbestos, which likewise reduces the dissipation of heat from said curved container part.

While we have shown and described and have pointed out in the annexed claims certain novel features of the invention it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its use and operation may be made by those skilled in the art without departing from the spirit and scope of the invention.

What we claim as new and desire -to secure by Letters Patent oi the United States is:-

i. A lamp unit comprising a gaseous electric discharge lamp device having a container consisting of two straight parts and a curved part connecting said straight parts, electrodes sealed into said container and a vaporizable material in said container, a heat conservator .in which said lamp device is mounted and a heat interceptor interposed between the curved part of said container and the ambient atmosphere.

2. A lamp unit comprising a gaseous electric discharge lamp device having a container consisting of two straight parts and a curved part connecting said straight parts, electrodes sealed into said container and a vaporizable material in saidcontainer, a double walled Jacket having the space between the inner and outer walls thereof evacuated and in which said lamp device is mounted and a heat interceptor interposed between the curved part oi said container and the ambient atmosphere.

3. A lamp unit comprising a gaseous electric discharge lamp device having a container consisting of two straight parts and a curved part connecting said straight parts, electrodes sealed into said container and a vaporizable material in said container, a double walled Jacket having the space between the inner and outer walls thereof evacuated and in which said lamp device is mounted and a reflecting coating on the curved part of said container to reduce the dissipation of heat from said curved part. 2

4. A lamp unit comprising a gaseous electric discharge lamp device having a container consisting of two straight parts and a curved part connecting said straight parts, electrodes sealed into said container and a vaporizable material in 2 said container, a double walled jacket having the space between the inner and outer walls thereof evacuated and in which said lamp device is mounted and a reflecting coating'on the part of said jacket adjacent the curved part of 3 said container.

5. A lamp unit comprising a gaseous electric discharge lamp device having a container consisting of two straight parts and a curved part connecting said straight parts, electrodes sealed 3 into said container and a vaporizable material in said container, a double walled jacket having the space between the inner and outer walls thereof evacuated and in which said lamp device is mounted and a coating of material having poor heat conducting characteristics on the curved part of said container.

6. A lamp unit comprising a gaseous electric discharge lamp device having a container consisting of two straight parts and a curved part 4 connecting said straight parts, electrodes sealed into said container and a vaporizable material in said container, a double walled jacket having the space between the inner and outer walls thereof evacuated and in which said lamp device is mounted and a coating of material having poor heat conducting characteristics on the part of said jacket adjacent the curved part of said container.

WILLEM UYTERHOEVEN. MARTINUS VAN DAM. CORNELIS VERBURG. 

